Overheating may contribute to sudden infant death

Published May 17, 2004; Category: DARTMOUTH MEDICAL SCHOOL

Overheating may contribute to sudden infant death 4 or 5 degrees too hot, and a baby can struggle to breathe

Dartmouth Medical School researchers have found that overheating just a few degrees could lead to sudden infant death syndrome (SIDS). The study, presented at the scientific program of The American Physiological Society in April, was designed to investigate a possible relationship between increased body temperature and SIDS.

Increasing the body temperature of newborn piglets by as little as four or five degrees Fahrenheit (2.5 to 3 degrees Centigrade) resulted in a substantially prolonged instability in control of breathing following a mild inhibitory stimulus, the study found.

SIDS remains the developed world's leading cause of postnatal infant mortality before the age of one year. Epidemiological evidence suggests heat stress may contribute to SIDS. SIDS occurrence is greater in the winter months, in both the Northern and Southern hemispheres, when infants are most likely to be covered with warm blankets, and elevated body temperature has been found in some infants even several hours after death from SIDS.

Piglets were studied by dropping a small volume of distilled water on the larynx, a standard method for inhibiting breathing and meant in this study to simulate the effects of mild regurgitation, a very common event in newborn humans. The piglets were not conscious. Inhibited breathing following the dropping of liquid on the larynx included coughing, swallowing and temporary cessation of breathing (apnea).

Three to five trials were conducted on each piglet before its temperature was raised by wrapping it in a heating blanket, which increased the heat slowly over about 30 minutes. The trials were then repeated, allowing time for full cooling back to the earlier body temperature between trials. In all the piglets, the higher body temperatures increased the instability of breathing following exposure to the water drops on the larynx. The change was particularly marked in the amount of time breathing ceased temporarily.

This raises the possibility that overheated infants may have abnormal responses to inhibitory stimuli, including simple regurgitation, says Aidan Curran, Assistant Professor in Physiology at DMS. He adds that regurgitation may lead to destabilization of the respiratory and/or cardiovascular systems leading to SIDS. He said he would like to see the response further studied, investigating the mechanism by which such a small change in body temperature can lead to such substantial effects on respiratory control.